Touch sensor and manufacturing method thereof

ABSTRACT

A touch sensor including a first substrate which extends in a first direction and on which first channels may be formed and stretched, a first conductive liquid injected into the first channels, a second substrate which extends in a second direction which intersects with the first direction and on which second channels may be formed and stretched, and a second conductive liquid injected into the second channels.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority from and the benefit of Korean PatentApplication No. 10-2015-0121938, filed on Aug. 28, 2015, which is herebyincorporated by reference for all purposes as if fully set forth herein.

BACKGROUND

Field

Exemplary embodiments relate to a touch sensor and a manufacturingmethod thereof.

Discussion of the Background

A touch sensor is an input device which, when touched by a human hand oran object, is capable of recognizing the location of the touch. Alongwith the advances in the development of smart devices, the usage andrequirements for touch sensors are on the rise.

Recently studies have been underway on flexible displays and stretchabledisplays. A stretchable touch sensor capable of being used as aninterface for a stretchable display has also been under development.

The above information disclosed in this Background section is only forenhancement of understanding of the background of the inventive concept,and, therefore, it may contain information that does not form the priorart that is already known in this country to a person of ordinary skillin the art.

SUMMARY

Exemplary embodiments provide to a touch sensor and a method ofmanufacturing the same which form channels that cross each other on astretchable substrate, where each of the channels includes a wedgehaving a round form. Because conductive liquid is injected into thechannel, touch sensitivity may increase as a result of the wedge. Inaddition, because there are no bubbles in the channel, damage to thesubstrate may be prevented.

Additional aspects will be set forth in the detailed description whichfollows, and, in part, will be apparent from the disclosure, or may belearned by practice of the inventive concept.

An exemplary embodiment discloses a touch sensor including a stretchablefirst substrate having first channels extended in a first direction, afirst conductive liquid injected into the first channels, a secondstretchable substrate having second channels extended in a seconddirection crossing the first direction, and a second conductive liquidinjected into the second channels.

An exemplary embodiment also discloses a method for manufacturing atouch sensor including forming a first groove-formed substrate havingfirst grooves, forming a first flat substrate, forming a first substratehaving first channels corresponding to the first groove by attaching thefirst groove-formed substrate and the first flat substrate, andinjecting a first conductive liquid into the first channels.

The foregoing general description and the following detailed descriptionare exemplary and explanatory and are intended to provide furtherexplanation of the claimed subject matter.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are included to provide a furtherunderstanding of the inventive concept, and are incorporated in andconstitute a part of this specification, illustrate exemplaryembodiments of the inventive concept, and, together with thedescription, serve to explain principles of the inventive concept.

FIG. 1, FIG. 2, and FIG. 3 are a perspective exploded view and twocross-sectional views illustrating a touch sensor in accordance with anexemplary embodiment.

FIG. 4A, FIG. 4B, and FIG. 5 are plan views illustrating an exemplaryembodiment of a structure of first channels and second channels of thetouch sensor shown in FIG. 1.

FIG. 6 is a plan view illustrating an exemplary embodiment of astructure of a wedge of the first channel shown in FIG. 4.

FIG. 7, FIG. 8, FIG. 9, FIG. 10, FIG. 11, FIG. 12, FIG. 13, FIG. 14,FIG. 15, FIG. 16, and FIG. 17 are cross-sectional views for describing amethod of manufacturing the touch sensor shown in FIG. 1.

FIG. 18 is a cross-sectional view for describing a touch sensor inaccordance with another exemplary embodiment.

FIG. 19 is cross-sectional views for describing a method ofmanufacturing a first flat substrate among the touch sensor shown inFIG. 18.

FIG. 20 and FIG. 21 are cross-sectional views for describing a method ofmanufacturing a third substrate among the touch sensor shown in FIG. 18.

FIG. 22 is a cross-sectional view for describing a touch sensor inaccordance with another exemplary embodiment.

FIG. 23 and FIG. 24 are cross-sectional views for describing a method ofmanufacturing the first groove-formed substrate of the touch sensorshown in FIG. 22.

DETAILED DESCRIPTION OF THE ILLUSTRATED EMBODIMENTS

In the following description, for the purposes of explanation, numerousspecific details are set forth in order to provide a thoroughunderstanding of various exemplary embodiments. It is apparent, however,that various exemplary embodiments may be practiced without thesespecific details or with one or more equivalent arrangements. In otherinstances, well-known structures and devices are shown in block diagramform in order to avoid unnecessarily obscuring various exemplaryembodiments.

In the accompanying figures, the size and relative sizes of layers,films, panels, regions, etc., may be exaggerated for clarity anddescriptive purposes. Also, like reference numerals denote likeelements.

When an element or layer is referred to as being “on,” “connected to,”or “coupled to” another element or layer, it may be directly on,connected to, or coupled to the other element or layer or interveningelements or layers may be present. When, however, an element or layer isreferred to as being “directly on,” “directly connected to,” or“directly coupled to” another element or layer, there are no interveningelements or layers present. For the purposes of this disclosure, “atleast one of X, Y, and Z” and “at least one selected from the groupconsisting of X, Y, and Z” may be construed as X only, Y only, Z only,or any combination of two or more of X, Y, and Z, such as, for instance,XYZ, XYY, YZ, and ZZ. Like numbers refer to like elements throughout. Asused herein, the term “and/or” includes any and all combinations of oneor more of the associated listed items.

Although the terms first, second, etc. may be used herein to describevarious elements, components, regions, layers, and/or sections, theseelements, components, regions, layers, and/or sections should not belimited by these terms. These terms are used to distinguish one element,component, region, layer, and/or section from another element,component, region, layer, and/or section. Thus, a first element,component, region, layer, and/or section discussed below could be termeda second element, component, region, layer, and/or section withoutdeparting from the teachings of the present disclosure.

Spatially relative terms, such as “beneath,” “below,” “lower,” “above,”“upper,” and the like, may be used herein for descriptive purposes, and,thereby, to describe one element or feature's relationship to anotherelement(s) or feature(s) as illustrated in the drawings. Spatiallyrelative terms are intended to encompass different orientations of anapparatus in use, operation, and/or manufacture in addition to theorientation depicted in the drawings. For example, if the apparatus inthe drawings is turned over, elements described as “below” or “beneath”other elements or features would then be oriented “above” the otherelements or features. Thus, the exemplary term “below” can encompassboth an orientation of above and below. Furthermore, the apparatus maybe otherwise oriented (e.g., rotated 90 degrees or at otherorientations), and, as such, the spatially relative descriptors usedherein interpreted accordingly.

The terminology used herein is for the purpose of describing particularembodiments and is not intended to be limiting. As used herein, thesingular forms, “a,” “an,” and “the” are intended to include the pluralforms as well, unless the context clearly indicates otherwise. Moreover,the terms “comprises,” “comprising,” “includes,” and/or “including,”when used in this specification, specify the presence of statedfeatures, integers, steps, operations, elements, components, and/orgroups thereof, but do not preclude the presence or addition of one ormore other features, integers, steps, operations, elements, components,and/or groups thereof.

Various exemplary embodiments are described herein with reference tosectional illustrations that are schematic illustrations of idealizedexemplary embodiments and/or intermediate structures. As such,variations from the shapes of the illustrations as a result, forexample, of manufacturing techniques and/or tolerances, are to beexpected. Thus, exemplary embodiments disclosed herein should not beconstrued as limited to the particular illustrated shapes of regions,but are to include deviations in shapes that result from, for instance,manufacturing. The regions illustrated in the drawings are schematic innature and their shapes are not intended to illustrate the actual shapeof a region of a device and are not intended to be limiting.

Unless otherwise defined, all terms (including technical and scientificterms) used herein have the same meaning as commonly understood by oneof ordinary skill in the art to which this disclosure is a part. Terms,such as those defined in commonly used dictionaries, should beinterpreted as having a meaning that is consistent with their meaning inthe context of the relevant art and will not be interpreted in anidealized or overly formal sense, unless expressly so defined herein.

FIGS. 1 to 3 are an exploded perspective view and two cross-sectionalviews illustrating a touch sensor in accordance with an exemplaryembodiment. FIG. 1 is an exploded perspective view illustrating thetouch sensor; FIG. 2 is a cross-sectional view illustrating the touchsensor viewed along section lines A-A′ and B-B′ of FIG. 1; and FIG. 3 isa cross-sectional view illustrating the touch sensor viewed alongsection lines C-C′ and D-D′.

Referring to FIG. 1, the touch sensor may include a first substrate 100,a second substrate 200, and a third substrate 300. The first substrate100, the second substrate 200, and the third substrate 300 may have athickness in the direction of a third direction which crosses both afirst direction and a second direction. The first substrate 100, thesecond substrate 200, and the third substrate 300 are separatelydescribed for ease of illustration, but in fact, the first substrate 100and the third substrate may be adhered together, and the third substrate300 and the second substrate may be adhered together. The firstsubstrate 100 may include first channels LC1 extending in the firstdirection, and a first conductive liquid may be inserted into the firstchannels LC1. The second substrate 200 may include second channels LC2extending in the second direction crossing the first direction, andsecond conductive liquid may be inserted into the second channels LC2.The third substrate 300 may be located between the first substrate 100and the second substrate 200. The first substrate 100 and the thirdsubstrate 300 may be adhered together, and the third substrate 300 andthe second substrate 200 may be adhered together. The first substrate100, the second substrate 200, and the third substrate 300 may all bestretchable, and in accordance with an exemplary embodiment, the elasticmodulus of the third substrate 300 may be lower than those of the firstsubstrate 100 and the second substrate 200. Alternatively, the materialmaking up the first substrate 100, the second substrate 200, and thethird substrate 300 may be the same, and the elastic moduli of the firstsubstrate 100, the second substrate 200, and the third substrate 300 mayall be the same. The material making up at least one among the firstsubstrate 100 to the third substrate 300 may include at least one of thegroups made up of polydimethylsiloxame (PDMS) or polyurethane, so thefirst substrate 100, the second substrate 200, and the third substrate300 may all be stretchable. Material making up at least one of the firstconductive liquid or the second conductive liquid may include at leastone from the group consisting of gallium (Ga) and indium (In).Particularly, if a eutectic gallium-indium alloy (Eutectic Ga—In,EGaIn), which is an alloy of eutectic method of gallium (Ga) and indium(In), is used, a liquid state with low resistivity may be maintained atroom temperature because the melting point of the alloy is lower thanroom temperature, making possible its use as the first conductive liquidor the second conductive liquid.

The first substrate 100, the second substrate 200, and the thirdsubstrate 300 will be explained in more detail with reference to FIGS. 2and 3. The first substrate 100 may include a first groove-formedsubstrate 100-H and a first flat substrate 100-F, and the secondsubstrate 200 may include a second groove-formed substrate 200-H and asecond flat substrate 200-F.

Referring to FIG. 2, first grooves may be formed on the firstgroove-formed substrate 100-H. A detailed explanation of the firstgroove-formed substrate 100-H will be given with reference to FIG. 9.The first flat substrate 100-F may be adhered to the first groove-formedsubstrate 100-H so that the first grooves are blocked from outside, andfirst holes may be formed on the first flat substrate 100-F. Firstelectrodes may be inserted into the first holes. For ease ofillustration, it may be assumed that the actual locations of A and A′within the device correspond to the locations of B and B′, and that onlya^(th) (where a is a natural number) first channel LC1-a among all firstchannels are shown here. Therefore, in FIG. 2, a first hole H1-a amongall the first holes is shown as a representative of the first holes, anda first electrode EC1-a among all the first electrodes are shown as arepresentative of the first electrodes. The first electrode EC1-a may bearranged between the first flat substrate 100-F and the third substrate300. When the touch sensor is driven, at least one of the firstelectrodes, for example the first electrode EC1-a, may be supplied witha pre-set voltage. When the first substrate of FIG. 1 is sectioned alongA-A′, the first channel LC1-a is divided by a greater number, but forease of illustration, the first channel LC1-a is divided by a smallernumber.

Referring to FIG. 3, second grooves may be formed on the secondgroove-formed substrate 200-H. The second flat substrate 200-F may beadhered to the second groove-formed substrate 200-H so that the secondgrooves are blocked from outside, and second holes are formed on thesecond flat substrate 200-F. Second electrodes may be inserted into thesecond holes. For ease of illustration, it may be assumed that theactual locations of C and C′ within the device correspond to thelocations of D and D′, and that only b^(th) (where b is a naturalnumber) second channel LC2-b among all second channels is shown here.Therefore, in FIG. 3, a second hole H2-b among all the second holes isshown as a representative of the second holes, and a second electrodeEC2-b among all the second electrodes is shown a representative of thesecond holes. The second electrode EC2-b may be arranged between thesecond flat substrate 200-F and the third substrate 300.

The touch sensor described with reference to FIGS. 1 to 3 may detecttouch in various ways. For example, when conductive material is touched,capacitance may be changed by the touch. Even when the same voltage issupplied by the first electrodes by changes in capacitance, levels ofcurrent or voltage measured by the second electrodes may be changed. Inother words, a touch sensor in accordance with an exemplary embodimentmay detect changes in current or voltage incurred by touch by conductivematerial. In addition, when pressure is applied to the touch sensor, thethickness T3 in the third direction of the point on the third substrate300 on which the pressure is applied may be changed, and the gap betweenthe first channels LC1 and the second channels LC2 may be changed.Capacitance may be changed due to changes in the gap, and thus, levelsof current or voltage measured by the first electrodes and the secondelectrodes may be changed. In other words, a touch sensor in accordancewith an exemplary embodiment may detect changes in current or voltageincurred by pressure. When a touch sensor in accordance with anexemplary embodiment is used, if it is lightly touched by conductivematerial and the capacitance is changed, or if, regardless of material,the thickness of the point on the third substrate 300 on which pressureis applied is changed by the pressure, the location of the touch, or thelocation of the point where the thickness has been changed, may becalculated. When the second substrate 200 shown in FIG. 1 is sectionedalong D-D′, the second channel LC2-b may be divided by a greater number,but for ease of illustration, the second channel LC2-b is divided by asmaller number.

FIGS. 4A, 4B, and 5 are plan views for describing an exemplaryembodiment of a structure of the first channels and the second channelsof the touch sensor of FIG. 1. FIGS. 4A and 4B are plan viewsillustrating an exemplary embodiment of a structure of the firstchannels of the touch sensor shown in FIG. 1, and FIG. 5 is a plan viewfor illustrating an exemplary embodiment of a structure of the secondchannels of the touch sensor of FIG. 1.

In FIGS. 4A and 4B, only two neighboring first channels among all thefirst channels are shown for ease of illustration. The first channelLC1-a may include a plurality of straight channels and wedges, and forease of illustration, only straight channels LC1-a-s-1 and LC1-a-s-2 anda wedge LC1-a-w-1 will be given as examples. Also, regarding the firstchannel LC1-(a+1), only the wedge LC1-(a+1)-w-2 will be explained. Thestraight channels LC1-a-s-1 and LC1-a-s-2 may extend in the seconddirection. In addition, the wedge LC1-a-w-1 of the first channel LC1-aand the wedge LC1-(a+1)-w-2 of the first channel LC1-(a+1), which areadjacent to each other, may be separated by a distance D. The wedgeLC1-a-w-1 may be a first wedge, and the wedge LC1-a+1-w-2 may be asecond wedge. The distance D may be equal to or greater than 150 μm andless than or equal to 200 μm. When the distance D is less than 150 μm,the distance between the side walls between the first channel LC1-a andthe second channel LC1-(a+1) may become undesirably short, increasingthe chance for the touch sensor to easily break. When the distance D isgreater than 200 μm, the accuracy of the touch sensor may decrease. Thewedge LC1-a-w-1 will be explained in more detail with reference to FIG.6.

In FIG. 5, only the second channel LC2-b among all the second channelsis shown for ease of illustration. The second channel LC2-b may includemultiple straight channels and wedges, but for ease of illustration,only straight channels LC2-b-s-1 and LC2-b-s-2 and wedges LC2-b-w-1 andLC2-b-w-2 will be given as examples. The straight channels LC2-b-s-1 andLC2-b-s-2 may extend in the first direction.

FIG. 6 is a plan view for describing an exemplary embodiment of astructure of a wedge of the first channel shown in FIG. 4.

In FIG. 6, only straight channels LC1-a-s-1 and LC1-a-s-2 and a wedgeLC1-a-w-1 are shown. The straight channel LC1-a-s-1 may have a width inthe first direction, and the width may be equal to or greater than 80 μmand less than or equal to 300 μm. The wedge LC1-a-w-1 may include around part, and the round part may include an inner round portion R-Iand an outer round portion R-O. The contact angle may be defined as theangle formed between a surface of a solid and a liquid when the liquidis in contact with the surface of the solid, and its value may bechanged depending on the kind of conductive liquid and material makingup the first substrate. When the wedge LC1-a-w-1 does not have an outerround portion R-O, slopes of the wedge LC1-a-w-1 may meet, forming anangle greater than 0 degrees (e.g., 22 to 45 degrees). If this angle isless than the contact angle between the first channels and the firstconductive liquid, not all of the conductive liquid may be injected intothe interface, and bubbles may be formed in the first channels. Whenbubbles are in the channels, the amount of the conductive liquid maydecrease, leading to a reduced sensitivity to touch and possibledestruction of the touch sensor due to the bubbles. However, as a wedgeLC1-a-w-1 has an outer round portion R-O, slopes of the wedge LC1-a-w-1may not meet forming an angle greater than 0 degrees. In addition,because the wedge LC1-a-w-1 has an inner round portion R-I, theinterface where the straight channels LC1-a-s-1 and LC1-a-s-2 and thewedge LC1-a-w-1 may not form an angle greater than 0 degrees (forexample, 22 to 45 degrees). Therefore, all the conductive liquid may beinjected into the interface, so no bubbles may form in the channels. Allof the conductive liquid may be injected into the inner round portionR-I, and it may be injected into the outer round portion R-O whencertain requirements for the radius of curvature (ROC) of the outerround portion R-O are met. In other words, wedges with round shapes maybe included, and conductive liquid may be injected into that channel, sosensitivity to touch may be improved by the wedge, but there may be nodamage to the substrate as there are no bubbles in the channel.

The wedge LC1-a-w-1 may have a length L in the second direction. Whenthe length L is less than 150 μm, channel resistance may increasecausing RC delay to worsen, and when the length L is greater than 600μm, the round part may become excessively large, causing channelsensitivity to decrease.

When the ROC is less than half of the width W of the straight channelsLC1-a-s-1 and LC1-a-s-2, the outer round portion R-O may be excessivelybent, which may cause all of the conductive liquid not to be injectedinto the outer round portion R-O, leading to the formation of bubbles.When there are bubbles present, the detecting sensitivity of the entiretouch sensor may be decreased, and the touch sensor may be damaged. Whenthe ROC of the outer round portion R-O is greater than 63% of the widthW of the straight channels LC1-a-s-1 and LC1-a-s-2, the outer roundportion R-O may become too flat, the length of the channels may beincreased, leading to an increase in resistance. As a result, thesensitivity of the touch sensor may be decreased. In other words, theROC of the outer round portion R-O may be expressed as the equationbelow:

0.5×W≦ROC−0≦0.63×W  [Equation 1]

(W: width of the straight channel LC1-a-s-1, ROC-O: ROC of the outerround portion R-O)

FIGS. 7 to 17 are cross-sectional views for describing a method ofmanufacturing the touch sensor shown in FIG. 1. FIGS. 7 to 14 arecross-sectional views for describing a method of manufacturing the firstsubstrate, and FIGS. 15 and 16 are cross-sectional views for describinga method of manufacturing the third substrate. A method of manufacturingthe second substrate may be described with reference to FIGS. 7 to 14.

FIG. 7 illustrates steps in forming first protrusions P on a mold M. Theshape of the first protrusions P may correspond to the shape of thefirst channels LC1 and the shape of the first grooves of the firstgroove-formed substrate 100-H, and the material making up theprotrusions P may be a material that is photosensitive and stackable toa substantial thickness. For example, SU-8, etc., may be included. Themold M may take the shape of a container later in order to hold fluid.

FIG. 8 illustrates a step in which material making up the firstgroove-formed substrate 100-H is injected into a mold M with the firstprotrusions P formed on it, is hardened, and forms the firstgroove-formed substrate 100-H. Material making up the firstgroove-formed substrate 100-H, for example polydimetylsiloxane (PDMS),may flow and be included as a liquid, However, if heat, ultravioletrays, etc. are applied, material making up the first groove-formedsubstrate 100-H may be hardened (curing). The first groove-formedsubstrate 100-H may be formed by putting the material making up thefirst groove-formed substrate 100-H into a mold M with the shape of acontainer and with the first protrusions P formed on it and hardeningusing the eternal environment (heat, ultraviolet rays, etc.). In otherwords, it may be hardened as the first grooves corresponding to thefirst protrusions P are formed.

FIG. 9 illustrates a step in which the first groove-formed substrate100-H is detached from the mold M. Applying external force onto thefirst groove-formed substrate 100-H may separate the mold M from thefirst groove-formed substrate 100-H, and the protrusions from the firstgroove-formed substrate 100-H. The steps shown in FIGS. 7 to 9 maycorrespond to the steps of forming the first groove-formed substrate100-H. The first grooves H of the first groove-formed substrate 100-Hmay correspond to the shape of the first protrusions P, and thethickness TH in the third direction of the first grooves H maycorrespond to the height in the third direction of the first channelsLC1.

FIG. 10 illustrates a step in which liquid material making up the firstflat substrate 100-F is poured into the mold M and is hardened. Materialmaking up the first flat substrate 100-F may possess the samecharacteristics as material making up the first groove-formed substrate100-H. Thus, repeated description may be omitted. The first flatsubstrate 100-F may be formed by pouring the material making up thefirst flat substrate 100-F into the mold M having the shape of acontainer and by hardening it by the external environment (heat,ultraviolet rays, etc.) Because the surface of the mold M touchingmaterial making up the first groove-formed substrate does not have anyprotrusions or grooves, the first flat substrate 100-F may have a flatshape.

FIG. 11 illustrates a step in which the first flat substrate 100-F isdetached from the mold M. Just like in the case of the firstgroove-formed substrate 100-H, application of external force onto thefirst flat substrate 100-F may separate the mold M and the first flatsubstrate 100-F. The steps shown in FIGS. 10 and 11 may correspond tothe step in which the first flat substrate is formed.

FIG. 12 illustrates a first adherence step in which the firstgroove-formed substrate 100-H and the first flat substrate 100-F areadhered together to form the first substrate with the first channelsformed on it. The first groove-formed substrate 100-H and the first flatsubstrate 100-F may be arranged in such a way that they are touchingeach other, applied heat to, and adhered together. Or the surface of thefirst groove-formed substrate 100-H which is to be attached and thesurface of the first flat substrate 100-F which is to be attached may beapplied with material making up the first groove-formed substrate 100-Hbefore it is hardened. When heat or ultraviolet rays are applied, thematerial making up the first groove-formed substrate 100-H may behardened, and the first groove-formed substrate 100-H and the first flatsubstrate 100-F may be adhered together. Alternatively, when materialmaking up the first groove-formed substrate 100-H and material making upthe first flat substrate 100-F are the same, the surfaces of the firstgroove-formed substrate 100-H and the first flat substrate 100-F may beoxygen plasma-treated, and the first groove-formed substrate 100-H andthe first flat substrate 100-F may be arranged in such a way that theyare touching each other. When the oxygen plasma-treated surfaces of thefirst groove-formed substrate 100-H and the first flat surface 100-Ftouch each other, the first groove-formed substrate 100-H and the firstflat substrate 100-F may be adhered together. The first channels LC1 maybe formed by the first groove-formed substrate 100-H and the first flatsubstrate 100-F being adhered together.

FIG. 13 illustrates a step in which first holes and temporary holes areformed in the first channels LC1, and first electrodes are inserted intothe first holes. The first holes and the temporary holes may be formedin the first channels, and the first electrodes may be inserted into thefirst holes. Because only the a^(th) first channel LC1-a is shown inFIG. 13, only a first hole H1-a among all the first holes is shown, onlya temporary hole HT-a among all the temporary holes is shown, and only afirst electrode EC1-a among all the first electrodes is shown in thefigure. Also, in accordance with an exemplary embodiment, the temporaryholes may not be formed. In FIG. 13, the first electrode EC1-a may notbe fixed with respect to the first substrate 100. In addition, tubes(not shown) may be inserted into the first and temporary holes to injectthe first conductive liquid into or to take air out of the firstchannels LC1. In this case, the first electrode EC1-a may be providedwithin one of the tubes.

FIG. 14 illustrates a step in which the first conductive liquid isinjected into the first channels through the first holes and gas istaken out of the first channels through the temporary holes. For ease ofillustration, explanations only regarding the first channel LC1-a amongall the first channels LC1 will be given. The first conductive liquidfrom one of the tubes inserted into the first hole H1-a may be injectedinto the first channel LC1-a. Concurrently, the air existent in thefirst channel LC1-a may be taken out of the first channel LC1-a throughone (not shown) of the tubes inserted into the temporary hole HT-a. Whenusing this method, no air may be left in the first channels LC1, makingpreventing the lowering of the sensitivity of the touch sensor anddamage to the touch sensor due to bubbles.

FIGS. 15 and 16 illustrate a method of manufacturing the thirdsubstrate.

FIG. 15 illustrates a step in which liquefied material making up thethird substrate 300 is poured into the mold and hardened. Since this isvery similar to the step described with reference to FIG. 10, in whichliquefied material making up the first flat substrate 100-F is pouredand hardened is very similar, the description thereof will be omitted.Material making up the third substrate 300 and capable of being includedin fluid may be put into a mold M with the shape of a container andhardened by the external environment (heat, ultraviolet rays, etc.) toform the third substrate 300. In accordance with an exemplaryembodiment, even when the material making up the first substrate 100,the second substrate 200, and the third substrate 300 may be the same,as the third substrate 300 is porous, the elastic modulus of the thirdsubstrate 300 may be lower than those of the first substrate 100 and thesecond substrate 200. Particularly, the material making up the thirdsubstrate 300 (for example, PDMS) may be poured into the mold M andstirred around to form foam. In order to form foam, other material (forexample, water) may additionally be injected into the mold M. Hardeningmaterial with foam formed may lead to the formation of a porous thirdsubstrate 300.

FIG. 16 illustrates a step in which the third substrate 300 is separatedfrom the mold M. As in the case of the first groove-formed substrate100-H, the mold M and the third substrate 300 may be separated byapplying external force to the third substrate 300.

FIG. 17 illustrates a third adhesion step in which the first substrateand the third substrate are adhered together. When material making upthe first substrate 100 and the third substrate 300 is the same, thefirst substrate 100 and the third substrate 300 may be adhered togetherthrough the methods described with reference to FIG. 12. The first andthe temporary holes may be isolated from outside by the third substrate300. In other words, the first conductive liquid injected into the firstchannels LC1 may not come outside.

After FIG. 17, the third substrate 300 and the second substrate 200 maybe adhered together through the methods described with reference to FIG.12. The second holes may be isolated from outside by the third substrate300. In other words, the second conductive liquid injected into thesecond channels LC2 may not come outside. After the adhesion of thethird substrate 300 and the second substrate 200, the touch sensor shownin FIGS. 1 to 3 may be obtained. It may be desirable for the firstchannels LC1 to extend in the first direction and for the secondchannels LC2 to extend in the second direction which crosses the firstdirection. If the third substrate 300 and the second substrate 200 areadhered together, the touch sensor described with reference to FIGS. 1to 3 may be completed.

FIG. 18 is a cross-sectional view for describing illustrates a touchsensor in accordance with another exemplary embodiment. The touch sensormay include a first substrate 100′, a second substrate 200′, and a thirdsubstrate 300′. The third substrate 300′ of the touch sensor shown inFIG. 18, unlike the one shown in FIG. 2 and FIG. 3, may includeprotrusions 300-p′. When the elastic modulus of the third substrate 300is lower than those of the first substrate 100 and the second substrate200, and when the third substrate 300′ includes protrusions 300-p′, thedegree that the protrusions 300-p′ are morphed may be greater than thatto which the a^(th) first channel LC1-a′ is morphed, even if pressure isapplied to the touch sensor. Therefore, the chance of a short circuitdue to blockage in channels may decrease as the degree to which thefirst channels LC1-a′ are morphed is reduced, even if the pressure isapplied.

FIG. 19 is cross-sectional views for describing a method ofmanufacturing the first flat substrate of the touch sensor of FIG. 18.Unlike FIG. 10, protrusions P′ may be formed on the mold M, and thematerial making up the first flat substrate 100-F and which may belongto liquid may be injected and hardened. Grooves may be formed on thefirst flat substrate 100-F′, and the shape of the grooves may correspondto the protrusions P′.

FIG. 20 and FIG. 21 illustrate how to manufacture the third substrate ofthe touch sensor of FIG. 18.

FIG. 20 illustrates a step in which material making up the thirdsubstrate 300 is injected between molds M2′ and M3′ with grooves formedon them and hardened to form the third substrate. The material making upthe third substrate 300′ may be injected among a fixing mold M1′ andmolds M2′ and M3′ with grooves H′ formed on them. Thereafter, whenforming the third substrate 300′ by hardening the material, theprotrusions corresponding to the grooves H′ may be formed on the thirdsubstrate 300′.

FIG. 21 illustrates a step in which the third substrate 300′ isseparated from the molds M2′ and M3′. As described with reference toFIG. 9, due to applying external force upon the third substrate 300′,the third substrate 300′ may be separated from the molds M1′, M2′, andM3′.

In addition to the methods described above, there are other methodswhich may be employed to form a third substrate with protrusions 300-p′formed on it. For example, as described with reference to FIGS. 15 and16, grooves may be formed after manufacturing the third substrate.

FIG. 22 is a cross-sectional view for describing a touch sensor inaccordance with another exemplary embodiment. In a touch sensor withreference to FIG. 22, the first groove-formed substrate 100-H″ mayinclude spacers Sp1-a″ and Sp2-a″. Because the spacers Sp2-a″ and Sp2-a″restrict the morphing of the first channels LC1-a″, short-circuiting ofchannels due to excessive applied pressure may be prevented. Also, whenpressure is applied to the touch sensor, the amount of change in thethickness of the third substrate 300″ may be greater than that of changein the thickness of the first substrate 100″ or the second substrate200″. Therefore, the gap between the first channels and the secondchannels may greatly be changed. Thus the sensitivity to changes in thelevel of current of voltage incurred by pressure may be increasedcompared to the touch sensor shown in FIG. 1.

FIGS. 23 and 24 are cross-sectional views illustrating some of themethods to manufacture the first groove-formed substrate of the touchsensor of FIG. 22.

FIG. 23 illustrates a step in which material making up the firstgroove-formed substrate 100-H″ is injected and hardened to form thefirst groove-formed substrate 100-H″. FIG. 23 is mostly identical toFIG. 8. It is different only in that first protrusions P″ are not formedin the part corresponding to the spacers A-sp1″ and A-sp2″.

FIG. 24 illustrates a step in which a first groove-formed substrate100-H″ is separated from a mold M″. FIG. 24 is similar to FIG. 9, anddiffers only in that spacers SP1-a″ and SP2-a″ are formed.

Exemplary embodiments provide a touch sensor and a method ofmanufacturing the same which form channels that cross each other on astretchable substrate, each of the channels including a wedge having around form. Because a conductive liquid is injected into the channel,touch sensitivity may increase due to the wedge, but because there areno bubbles in the channel, damage to the substrate may be prevented.

Although certain exemplary embodiments and implementations have beendescribed herein, other embodiments and modifications will be apparentfrom this description. Accordingly, the inventive concept is not limitedto such embodiments, but rather to the broader scope of the presentedclaims and various obvious modifications and equivalent arrangements.

What is claimed is:
 1. A touch sensor comprising: a first stretchablesubstrate comprising first channels extended in a first direction; afirst conductive liquid injected into the first channels; a secondstretchable substrate comprising second channels extended in a seconddirection crossing the first direction; and a second conductive liquidinjected into the second channels.
 2. The touch sensor as claimed inclaim 1, wherein: at least one of the first channels or the secondchannels comprises straight lines and wedges, and at least one of thewedges comprises a round part; the round part comprises an inner roundportion and an outer round portion; and a radius of a curvature of theouter round is expressed in an equation below:0.5×W≦ROC−0≦0.63×W (where W is at least one width of the straight linesand ROC-O is the radius of the curvature of the outer round portion). 3.The touch sensor as claimed in claim 2, wherein: two adjacent firstchannels among the first channels comprise a first wedge and a secondwedge, respectively; the first wedge and the second wedge are adjacentto each other; at least one of a length in the second direction of thefirst wedge and the second wedge is greater than or equal to 150 μm andless than or equal to 600 μm; and a distance between the first wedge andthe second wedge is greater than or equal to 150 μm and less than orequal to 200 μm.
 4. The touch sensor as claimed in claim 1, wherein thetouch sensor further comprises: first electrodes inserted into firstholes formed at one end of the first channels; and second electrodesinserted into second holes formed at one end of the second channels,wherein: a voltage having a preset level is supplied to at least one ofthe first channels; at least one level of current or voltage among thesecond electrodes is changed due to a change in capacitance when aconductive material touches the touch sensor; and a touch position isdetected based on the change in level of the current or voltage.
 5. Thetouch sensor as claimed in claim 4, wherein: the touch sensor furthercomprises a third stretchable substrate disposed between the firststretchable substrate and the second stretchable substrate; and thethird substrate blocks the first holes and the second holes fromoutside.
 6. The touch sensor as claimed in claim 5, wherein: the thirdstretchable substrate has a thickness in a third direction crossing thefirst direction and the second direction; and when an external force isapplied to the touch sensor, the capacitance between the firstconductive liquid and the second conductive liquid changes as a resultof the change in the thickness, the level of current or voltage measuredby the first electrodes or the second electrodes is changed as a resultof the change in the capacitance, and the touch position is detectedbased on the change in the level of the current or voltage.
 7. The touchsensor as claimed in claim 5, wherein: a material forming at least oneof the first stretchable substrate to the third substrate comprises atleast one from a group consisting of polydimethylsiloxane (PDMS) orpolyurethane; and a material forming at least one of the firstconductive liquid or the second conductive liquid includes at least onefrom a group consisting of gallium (Ga) or indium (In).
 8. The touchsensor as claimed in claim 5, wherein: an elastic modulus of the thirdsubstrate is lower than an elastic modulus of the first substrate and anelastic modulus of the second substrate; and the third substrate isporous.
 9. The touch sensor as claimed in claim 5, wherein the thirdsubstrate comprises a protrusion.
 10. The touch sensor as claimed inclaim 4, wherein: the first stretchable substrate comprises: a firstgroove-formed substrate comprising first grooves that are a portion ofthe first channels; and a first flat substrate attached to the firstgroove-formed substrate and configured to block the first grooves fromoutside and comprising the first holes; and the second substratecomprises: a second groove-formed substrate comprising second groovesthat are a portion of the second channels; and a second flat substrateattached to the second groove-formed substrate and configured to blockthe second grooves from outside and comprising the second holes.
 11. Thetouch sensor as claimed in claim 10, wherein at least one of the firstgroove-formed substrate and the second groove-formed substrate furthercomprises a spacer configured to restrict morphing of the first channelsor the second channels.
 12. A method for manufacturing a touch sensor,the method comprising: forming a first groove-formed substratecomprising first grooves; forming a first flat substrate; forming afirst substrate comprising first channels corresponding to the firstgroove by attaching the first groove-formed substrate and the first flatsubstrate; and injecting a first conductive liquid into the firstchannels.
 13. The method as claimed in claim 12, wherein: at least oneof the first channels comprises straight lines and wedges, each of thewedges comprising a round part; the round part comprises an inner roundportion and an outer round portion; and a radius of a curvature of theouter round is expressed in an equation below:0.5×W≦ROC−0≦0.63×W (where W is at least one width of the straight linesand ROC-O is the radius of the curvature of the outer round portion).14. The method as claimed in claim 12, wherein the forming of the firstgroove-formed substrate comprises: forming the first groove-formedsubstrate; forming first protrusions on a mold; injecting a materialforming the first groove-formed substrate into the mold comprising thefirst protrusions; forming the first groove-formed substrate byhardening the injected material; and separating the first groove-formedsubstrate and the mold, wherein a shape of the first protrusionscorresponds to the first grooves.
 15. The method as claimed in claim 12,further comprising: forming a second groove-formed substrate comprisingsecond grooves; forming a second flat substrate; forming a secondsubstrate comprising second channels corresponding to the second grooveby attaching the second groove-formed substrate and the second flatsubstrate; injecting a second conductive liquid into the secondchannels; and fixing the first substrate onto the second substrate,wherein, in the fixing, the first channels and the second channels arefixed such that the first channels extend in a first direction and thesecond channels extend in a second direction crossing the firstdirection.
 16. The method as claimed in claim 15, wherein: the fixingcomprises: forming a third substrate; attaching the first substrate andthe third substrate; and attaching the third substrate and the secondsubstrate; and the third substrate has a thickness in a third directioncrossing the first direction and the second direction; and when thethickness is changed by an external force, a capacitance between thefirst conductive liquid and the second conductive liquid is changed. 17.The method as claimed in claim 16, wherein the forming of the thirdsubstrate comprises: injecting a material forming the third substrateinto a mold and forming bubbles; forming the third substrate byhardening the material; and separating the third substrate from themold.
 18. The method as claimed in claim 16, wherein the forming of thethird substrate comprises: injecting a material forming the thirdsubstrate between molds comprising grooves; forming the third substrateby hardening the material; and separating the third substrate from themolds.
 19. The method as claimed in claim 16, wherein the injecting ofthe first conductive liquid comprises: forming first holes at one end ofthe first channels, forming temporary holes at the other end of thefirst channels, and inserting first electrodes into the first holes; andinjecting the first conductive liquid into the first channels throughthe first holes and discharging gas in the first channels through thetemporary holes.
 20. The method as claimed in claim 19, wherein, in theattaching of the first substrate and the third substrate, the firstholes are blocked from outside by the third substrate.